Windows Pairing Screen Becomes Unresponsive

I found myself in a situation in which the Windows implementation of Zwift become unresponsive while at the pairing screen. After playing around with it for a while, it appears to have something to do with the Beta Bluetooth Functionality while also having an Ant+ stick in a USB port.

I am able to reproduce the issue with the following steps:

  1. Insert an Ant+ stick into a USB port.
  2. Launch Zwift.
  3. Enable Beta Bluetooth Functionality.
  4. Exit and Relaunch Zwift.
  5. Immediately regret previous decisions. The app is now unresponsive.
  6. Unplug the Ant+ stick.
  7. Everything is now fine.

Note that the UI is (mostly) unresponsive. It will update once every 20 or 30 seconds, so it can take a while to respond to mouse clicks. My guess is it’s hanging while performing device discovery. If so, perhaps you should consider moving device discovery to it’s own thread instead of blocking the user interface thread (because an unresponsive UI is super annoying). The process is not CPU bound, only consuming about 10% CPU.

All software is up-to-date as of today (June 6, 2019): Zwift, Windows 10, Bluetooth Drivers. Also, the system is more than capable of running Zwift: 6 Core Intel Coffee Lake CPU, NVidia 1080ti GPU, NVME SSD primary storage.

I’m experiencing the same problems. Sometimes a reboot helps, but this morning it took me about 15 minutes to launch an instance of that app that would pair with ANT+. I don’t need to use Bluetooth, so might disable the feature and see if it goes back to normal.

Everything had been running fine fine for almost 3 months until the most recent update threw this issue in the mix.

This has started happening for me recently in the last two weeks or thereabouts. Sometimes it’s fine, others it’s not.

On Sunday, I was all paired up, ready to roll, as the counter got to about 3 seconds to go, the app froze for a few seconds, and then all ANT+ connections died. I had to restart Zwift to get going again, obviously if it were a race, that’d be my race over.

Today, it would freeze up with two ANT+ sticks connected; removing one would fix it, but it’s not specific to the ANT+ stick, as I’ve had this issue with each of them.